The main objective of this longstanding research program, which was voluntarily interrupted in 2008, remains the elucidation of principles governing prenatal development of the primate visual system. Accumulated evidence indicates that the developing human visual system has a number of anatomical, cellular and molecular features that are underdeveloped or absent in non-primate species. It is generally agreed that genes and transcription factors activated sequentially before birth specify these features, although no specific details are available. To shed light on these questions, we propose to perform a comprehensive analysis of gene expression by next generation sequencing in visual structures at different stages of development of the macaque monkey. We selected this Old World monkey as the main study subject because its visual system is remarkably similar to that in humans, and contains features that are underdeveloped or absent in non-primate species and thus cannot be studied in more common animal models. We propose to take advantage of our unique experience, access to the human material and the primate breeding colony at Yale as well as already collected tissue, to apply the methodological advances made in genetics and molecular biology to characterize and analyze development of these features. To obtain the most from the expensive animals and valuable tissue, we will study the entire system, from the retinal (Aim #1) via the thalamus (Aim #2) to the areas 17 and 18 of the visual cortex (Aim #3) including possible contribution from the subpial granular layer (Aim #4). At each level we will use immunocytochemistry, in situ hybridization, confocal microscopy and mRNA seq gene profiling following laser capture microdissection of selected populations of cells in human, macaque and mouse developing visual system. As a next step, we will carry out experimental studies in the developing macaque brain and supravital human embryonic brain tissue, including application of transneuronal tracers or lentiviral gene transfer, to identify molecular and cellula mechanisms involved in ontogenetic and phylogenetic emergence of these differences. Understanding the uniqueness of the primate visual system will provide an essential bridge between fundamental research on the visual system obtained from non-primate species and the primate and human emerging properties. These data have potential to benefit, research on primate anatomy, physiology and behavior as well as the neuropathology of normal and disordered human brain. Finally, taking advantage of the data from the macaque genome project, our findings may provide insight into genetic and acquired congenital errors of primate visual system development.